<p>The failure of engineering rock masses is a progressive mechanical process, the distinct anisotropic structure of leads to complex failure responses. These responses differ significantly from those of anisotropic rocks with macroscopic bedding (ARMB). However, the fracture evolution of anisotropic rock with direction-arranged minerals (ARDAM) remains insufficiently understood. To explore the fracture characteristics of ARDAM after progressive failure, the biotite quartz schist, a typical ARDAM material with different schistosity angles, was used to conduct triaxial cyclic loading tests under various confining pressures and CT scanning tests. The 3D reconstruction and parameter extraction of cracks were then completed by an improved technique for identifying cracks. This study explored the influence of confining pressure and schistosity angle on fracture evolutions, and analyzed the differences in fracture characteristics between two anisotropic rocks with direction-arranged minerals and macroscopic beddings, respectively. Results show that the failure modes transition from tensile-shear mixed failure to shear-slip failure to typical shear failure with increasing schistosity angle, and these transitions are associated with a distinct U-shaped trend in crack morphology and crack distribution parameters. As confining pressure increases, crack propagation modes transition from intergranular expansion to Y-shaped transgranular expansion, ultimately forming a network-like transgranular structure. The evolution of cracks reveals the macroscopic fracture phenomenon of ARDAM, which ranges from brittle to ductile failure. The fracture characteristics in ARDAM are minimally influenced by varied confining pressure, whereas there is a strong influence in ARMB. This study offers a theoretical foundation for understanding directional reinforcement and fracture behavior in schist engineering.</p>

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Fracture Characteristics and Quantitative Analysis of Anisotropic Rock with Direction-Arranged Minerals Subjected to Triaxial Cyclic Loading: A Case of Biotite Quartz Schist

  • Han Bao,
  • Yankai Wang,
  • Changqing Liu,
  • Qun Qi,
  • Hengxing Lan,
  • Shengwen Qi,
  • Bo Li,
  • Peng Sha,
  • Hongtao Lv

摘要

The failure of engineering rock masses is a progressive mechanical process, the distinct anisotropic structure of leads to complex failure responses. These responses differ significantly from those of anisotropic rocks with macroscopic bedding (ARMB). However, the fracture evolution of anisotropic rock with direction-arranged minerals (ARDAM) remains insufficiently understood. To explore the fracture characteristics of ARDAM after progressive failure, the biotite quartz schist, a typical ARDAM material with different schistosity angles, was used to conduct triaxial cyclic loading tests under various confining pressures and CT scanning tests. The 3D reconstruction and parameter extraction of cracks were then completed by an improved technique for identifying cracks. This study explored the influence of confining pressure and schistosity angle on fracture evolutions, and analyzed the differences in fracture characteristics between two anisotropic rocks with direction-arranged minerals and macroscopic beddings, respectively. Results show that the failure modes transition from tensile-shear mixed failure to shear-slip failure to typical shear failure with increasing schistosity angle, and these transitions are associated with a distinct U-shaped trend in crack morphology and crack distribution parameters. As confining pressure increases, crack propagation modes transition from intergranular expansion to Y-shaped transgranular expansion, ultimately forming a network-like transgranular structure. The evolution of cracks reveals the macroscopic fracture phenomenon of ARDAM, which ranges from brittle to ductile failure. The fracture characteristics in ARDAM are minimally influenced by varied confining pressure, whereas there is a strong influence in ARMB. This study offers a theoretical foundation for understanding directional reinforcement and fracture behavior in schist engineering.